The oxidation state of fluorine is -1. Oxidation numbers are assigned based on electronegativity periodic trends. Atoms with large electronegativities have negative oxidation numbers, and fluorine is the most electronegative atom on the periodic table.
Fluorine is a chemical element with an atomic number of 9. It exists at room temperature as a pale yellow, diatomic gas that is highly toxic. As the most electronegative atom on the periodic table, fluorine is highly reactive, and it can form compounds with almost every other atom on the periodic table. It can even form compounds with some of the inert noble gases.